A known detection circuit detecting a physical quantity of a detection target by a detection element, for example, a semiconductor strain gauge, is proposed (For example, refer to JPS61-28081A (hereinafter referred to as Patent reference 1) and JP2011-242312A (hereinafter referred to as Patent reference 2)). The detection circuit outputs detection signals that are in response to a terminal voltage of the detection element.
Meanwhile, the terminal voltage of the detection element is defined by a resistance value of the detection element and a current (a constant current) supplied to the detection element. The current supplied to the detection element may vary due to the change of the temperature level or the mixture of noises. Accordingly, the variance of the current due to the change of the temperature level or the mixture of noises is desired to be inhibited.
A need thus exists for a current source circuit and a detection circuit which is not susceptible to the drawback mentioned above.